Top Letter

INVICTA INVESTIGATION: A NEW THEORY

In Thomas Bright’s article about the fascinating one-off locomotive Invicta (SR477), he rightly raises the question as to why the boiler was converted from being multi-tubed, like its famous Rocket contemporary, to having a single unidirectional flue in a boiler shell extended by a further ring. A retrograde step. Last year, I wrote to Dr Michael Bailey who authored the book Loco Motion, The World’s Oldest Steam Locomotives. In the feature on Invicta the boiler alterations are said to have been “for reasons that have never been satisfactorily explained”. Being involved with the Keighley & Worth Valley Railway’s water treatment regime, it was my suggestion to him that, whereas Rocket and its sisters had been running on the softer water coming down from the Pennines, that found around Canterbury was much harder and the operators would have quickly experienced issues of scaling which would foul the waterways and the tube nest for which they were unprepared. Quite possibly this would have led not only to poor steaming, but overheating and possibly buckling of the boiler and firebox platework. The alterations to the boiler, therefore, should be seen as trying to make the best out of a bad job. I am sure that Dr Bailey will not mind me quoting from his reply: “I think your analysis is almost certainly correct… Further evidence for this comes just a few months later, on the Leicester & Swannington Railway, which experienced similar problems from hard water. In that case Robert Stephenson came to an early understanding of the problem and introduced a policy of gathering rainwater in large quantities with which to provide a supply for its locomotives. “Had he had time to appreciate the problem on Invicta he might have introduced a similar initiative which would have been a lot cheaper than re-making the boiler!” Ralph Ingham, Loco Dept Secretary, KWVR

OPERATORS WOULD HAVE EXPERIENCED SCALING